Prepare the Marinade. Start by soaking the dried chiles in hot water for about 15 minutes to soften them. Drain and blend them with pineapple juice, vinegar, garlic, onion, and spices until smooth.
Marinate the Pork. Place the thinly sliced pork shoulder in a large dish or resealable bag and pour the marinade over the top. Make sure the pork is well-coated. Cover and refrigerate for at least 4 hours or, even better, overnight.
Cook the Pork. Preheat your skillet over medium-high heat. Cook the marinated pork slices in batches until they are charred and cooked through, about 3-5 minutes per side.
Grill the Pineapple. While the pork is cooking, grill slices of fresh pineapple until caramelized and juicy. Dice into bite-sized pieces for topping.
Assemble the Tacos. Warm the corn tortillas and fill each with juicy Pork Al Pastor. Top with grilled pineapple, diced onion, and fresh cilantro. Add a squeeze of lime for extra brightness.